I’ve had 983 front panel designs fabbed in PCB material, FR4 (OK, 983 may be an exaggeration). Never a problem until my order in November when JLCPCB’s reviewer emailed:
As shown below, the maximum plated drill size we can do is 6.3mm, should we make the indicated holes as non-plated?
That was startling. The indicated holes are for 1/4″ jacks and are 10 mm diameter. They’d done plated through jack holes on every panel before this. (Oddly, the reviewer’s email referred to only one of several panels in my order, no objections to the others.) I mentioned this in my reply and they said:
Our capability is 6.3mm. If we do 10 mm plated through hole, the quality not guaranteed. If you can accept the risk of bad quality we can continue proceed with 10 mm plated through hole.
Meanwhile I checked their website and sure enough, they say they can do plated holes up to 6.3 mm. I’d never noticed that before. In fact, it says the maximum drill size is 6.3 mm. And I checked several other fabricators and all of them say maximum drill size 6.3 mm.
Obviously they can make round holes larger than that, but by milling, not drilling. I’d been using custom KiCad footprints for pads with larger holes, specified in the drill file. But apparently JLCPCB had just been moving such holes to the edge cuts layer to be milled.
Anyway, I told them either plated through or not was okay with me, as long as the mounting slots in the corners were plated through. All of them came in with entirely satisfactory plated through holes.
No big deal in the end, but I figured if in the future I could avoid this issue holding up an order that would be good, and in any case I really ought to not be submitting designs that violate their stated capabilities. I noticed KiCad had mounting hole footprints looking like this:
KiCad footprint MountingHole_8.4mm_M8_Pad_Via
the idea being, I think, that through plating could be damaged by a screw being inserted and removed, so plated through vias are added around the hole to maintain the connection between the front and back planes. It’s still a plated through pad hole in the center, though.
You’d think you could take that footprint design and just change the hole from PTH to NPTH, wouldn’t you? But no, KiCad doesn’t let you do that in any easy way, and even if it did the large hole would still be in the drill file. So it took more effort, but I did come up with a new library of footprints for panel components where the large holes are drawn on the edge cuts layer and are surrounded by plated vias. One oddity is that in KiCad 6 some of the pad numbers displayed in the PCB editor come out sideways, but not in the newly released KiCad 7. Another is that the vias do not appear in the 3D viewer:
Jack hole in 3D viewer
But they’re really there anyway.
While I was at it I re-examined the hole diameters I was using. I found sites online giving recommended hole diameters for various standard imperial and metric bushings, and went by them. Some of the diameters I’d been using were pretty much spot on, but some were too loose and some too tight.
In my most recent fab order I got PCBs for three modules but a panel for only one (a fourth module, whose PCB I already had). I didn’t want to order multiple panels until I’d gotten one done with the new footprints and seen how it went. Here it is:
Analog Output 